1. The Field of the Invention
This invention relates to anesthetic systems and more particularly to that class providing a closed exhaust discharge path for waste gases.
2. Description of the Prior Art
The prior art includes semi-closed and closed exhaust systems for disposing the waste gas products from anesthesia machines. U.S. Pat. No. 3,276,446 issued on Oct. 4, 1966 to W. W. Hay teaches a semi-closed anesthetic system utilizing a relief valve scheme for permitting the waste gases or administered gases, when exceeding a predetermined pressure level, to be vented to the atmosphere. The difficulty encountered with this invention is that operating room personnel, in proximity to the anesthesia machine, suffer pharmocological effects, such as discomfort or even cytotoxcity. Birth defects of the children of hospital personnel routinely exposed to waste gases admitted to the atmosphere is discussed by Corbett, T. H., Cornell, R. G., Endres, J. L., Leeding, K., "Birth Defects Among Children of Nurse Anesthetists." Anesthesiology 41: 341 -344, 1974. U.S. Pat. No. 3,604,488 issued on Sept. 14, 1971 to R. A. Marrese et. al. discloses a relief valve for an anesthetic gas line which can be utilized to conventionally discharge over-loading anesthetic gas into the surrounding atmosphere, and which further is provided with a valve assembly for connection to a closed system so that the over-loading anesthetic gas is retained with the closed system and is not discharged to the surrounding atmosphere. Manual operaton of the valve selects between the two modes of waste gas removal. Both of the aforementioned patents suffer the common deficiency in which high levels of toxic gases may accumulate in the operating theater.